1. Field of the Invention
This invention relates to hydraulic couplings. More particularly, it relates to pressure-balanced undersea hydraulic couplings.
2. Description of the Related Art
A wide variety of hydraulic coupling members adapted for use in the subsea environment are known and used. In a basic coupling, the probe of the male member may act as a piston in an hydraulic cylinder—the cylinder being the receiving chamber of the female member. Hydraulic fluid under pressure exerts a force on the male probe proportional to its cross-sectional area. This force tends to push the probe of the male member out of the receiving chamber of the female member. Since a hydraulic system may be pressurized when coupling members are joined, this piston action can significantly increase the force necessary to make up the connection. This is especially problematic in undersea applications because couplings must often be made up using remotely operated vehicles (ROV's). A plurality of hydraulic couplings are often made up together on a manifold plate. Thus, the mating force required can be significant, necessitating larger and more powerful ROVs to accomplish.
In response to this problem, a number of pressure-balanced hydraulic couplings have been developed. The design of a pressure-balanced coupling is such that the system hydraulic pressure does not act differentially on the cross section of the male probe. The following patents of National Coupling Company (Stafford, Tex.) describe pressure-balanced couplings:
U.S. Pat. Nos. 5,099,882 and 5,203,374 entitled “Pressure balanced hydraulic coupling with metal seals” (which are related to one another) disclose a pressure-balanced hydraulic coupling for use in undersea drilling and production operations. The coupling has radial passageways communicating between the male and female members such that substantial fluid pressure is not exerted against the face of either member during coupling or uncoupling or during the coupled state. Check valves in both the male and female members are opened when the male member probe is fully inserted into the receiving chamber of the female member. Mutually opposed valve actuators contact one another to effectuate the simultaneous opening of each check valve, and allow fluid to flow through a valve port and then radially through matching fluid passageways in the male and female members. The radial passageways of the male and female members match up at their longitudinal surfaces so that fluid pressure between the male and female members is in a substantially radial direction and is not exerted at the face of either member. A first pair of seals is positioned on each side of the radial passage for sealing between the receiving chamber and the seal retainer. A second pair of seals is positioned on each side of the radial passage for sealing between the seal retainer and the male member. The seals are pressure-energized metal seals.
U.S. Pat. No. 6,202,690 entitled “Pressure balanced undersea hydraulic coupling” discloses an undersea hydraulic coupling is pressure balanced to reduce forces tending to urge the coupling members apart during coupling or uncoupling. A seal retainer having an L-shaped fluid passage is used to provide fluid communication between the radial fluid passage in the male member and the longitudinal fluid passage in the female member of the coupling. The seal retainer holds one or more radial seals in the female member upon disengagement of the male coupling member.
U.S. Pat. No. 6,123,103 entitled “Pressure balanced coupling with split body” discloses a pressure balanced hydraulic coupling for use in undersea drilling and production operations that has radial passages connecting between the male and female members such that fluid pressure is not exerted against the face of either member during coupling or uncoupling. The female member has a split body with a first part and a second part, each having a longitudinal passage and a radial fluid passage. A radial seal is positioned on the junction between the first and second parts of the female member body to facilitate removal and replacement of the radial seal when the split body is disassembled. The male member may be inserted through the first and second parts of the female coupling member, thereby establishing fluid communication between the coupling members in a direction transverse to the coupling member bores.
U.S. Pat. No. 5,360,035 entitled “Pressure balanced poppet valve for hydraulic couplings” discloses an undersea hydraulic coupling having a poppet valve movable between an open and a closed position that operates without substantial fluid pressure exerted axially against the face of the poppet valve. When the poppet valve is opened, radial passages are interconnected through an annular cavity between the poppet valve body and the valve bore.
U.S. Patent Application Publication No. US 2005/0029749 discloses an undersea hydraulic coupling member having a bore liner that protects the coupling members from galling during assembly or disassembly. The bore liner is removable from the bore of a female undersea hydraulic coupling member. The bore liner may be integral with a seal section that may seal with a male undersea hydraulic coupling member. The bore liner also may have an outer diameter configured to engage and interlock with the bore in which the bore liner is positioned. In certain embodiments, the bore liner is fabricated from PEEK.
Pressure balanced couplings are generally more complex and more difficult to manufacture than non-pressured balanced couplings. A simplified pressure-balanced coupling would be advantageous. As space for coupling members on manifold plates and tubing hangars becomes ever more restricted, a need exists for a smaller, less complex pressure balanced coupling. A pressure balanced coupling with a bore liner also represents a needed improvement.